Effect of Continuous Application of Low-Acidulent Fertilizer on Acidification of an Andisol and Plant Growth

Our objective was to prevent the soil acidification caused by the NH4  + and the accumulation of SO4  2− and Cl− using a low acidulent urea based fertilizer applied in an Andisol that initial pH was adjusted to pH5 (named LAF5) or pH6 (named LAF6) in comparison with the continuous application of a rapidly soluble ammonium based fertilizer (RSF) applied on the same soils (named RSF5 and RSF6, respectively). Komatsuna (Brassica campestris var. maruha) and barley (Hordeum vulgare L.) were used as test plants. After three successive Komatsuna cultivations, barley seedlings were grown for 7 days to evaluate the degree of soil acidification. A rate of 0.2 g N kg−1 soil of each fertilizer was applied in each Komatsuna culture. No accumulation of sulfate and chloride ions was found in the soil continuously treated with the LAF. However, the continuous applications of RSF accumulated both sulfate and chloride, and lowered the soil pH remarkably compared to those of LAF. Initial soil extractable SO4  2− contents in...